Top Description Methods
javax.persistence

public @Interface MapKeyJoinColumn

extends Annotation
Annotations
@Repeatable:MapKeyJoinColumns
@Target:METHOD, FIELD
@Retention:RUNTIME
Imports
java.lang.annotation.Repeatable, .Target, .Retention
Specifies a mapping to an entity that is a map key. The map key join column is in the collection table, join table, or table of the target entity that is used to represent the map. If no MapKeyJoinColumn annotation is specified, a single join column is assumed and the default values apply. 

   Example 1:

   @Entity
   public class Company {
      @Id int id;
      ...
      @OneToMany   // unidirectional
      @JoinTable(name="COMPANY_ORGANIZATION",
                 joinColumns=@JoinColumn(name="COMPANY"),
                 inverseJoinColumns=@JoinColumn(name="VICEPRESIDENT"))
      @MapKeyJoinColumn(name="DIVISION")
      Map<Division, VicePresident> organization;
   }

   Example 2:

   @Entity
   public class VideoStore {
      @Id int id;
      String name;
      Address location;
      ...
      @ElementCollection
      @CollectionTable(name="INVENTORY",
                       joinColumns=@JoinColumn(name="STORE"))
      @Column(name="COPIES_IN_STOCK")
      @MapKeyJoinColumn(name="MOVIE", referencedColumnName="ID")
      Map<Movie, Integer> videoInventory;
      ...
    }

    @Entity
    public class Movie {
       @Id long id;
       String title;
       ...
    }

    Example 3:

    @Entity
    public class Student {
       @Id int studentId;
       ...
       @ManyToMany  // students and courses are also many-many
       @JoinTable(name="ENROLLMENTS",
                  joinColumns=@JoinColumn(name="STUDENT"),
                  inverseJoinColumns=@JoinColumn(name="SEMESTER"))
       @MapKeyJoinColumn(name="COURSE")
       Map<Course, Semester>  enrollment;
       ...
    }
Since
Java Persistence 2.0
See Also
ForeignKey

Method Summary

Modifier and TypeMethod and Description
public String
columnDefinition()

(Optional) The SQL fragment that is used when generating the DDL for the column.

public ForeignKey
foreignKey()

(Optional) Used to specify or control the generation of a foreign key constraint when table generation is in effect.

public boolean
insertable()

(Optional) Whether the column is included in SQL INSERT statements generated by the persistence provider.

public String
name()

(Optional) The name of the foreign key column for the map key.

public boolean
nullable()

(Optional) Whether the foreign key column is nullable.

public String
referencedColumnName()

(Optional) The name of the column referenced by this foreign key column.

public String
table()

(Optional) The name of the table that contains the foreign key column.

public boolean
unique()

(Optional) Whether the property is a unique key.

public boolean
updatable()

(Optional) Whether the column is included in SQL UPDATE statements generated by the persistence provider.

Inherited from java.lang.annotation.Annotation:
annotationTypeequalshashCodetoString

Method Detail

columnDefinitionback to summary
public String columnDefinition()

(Optional) The SQL fragment that is used when generating the DDL for the column. Defaults to SQL generated by the provider for the column.

foreignKeyback to summary
public ForeignKey foreignKey()

(Optional) Used to specify or control the generation of a foreign key constraint when table generation is in effect. If this element is not specified, the persistence provider's default foreign key strategy will apply.

Since
Java Persistence 2.1
insertableback to summary
public boolean insertable()

(Optional) Whether the column is included in SQL INSERT statements generated by the persistence provider.

nameback to summary
public String name()

(Optional) The name of the foreign key column for the map key. The table in which it is found depends upon the context.

  • If the join is for a map key for an element collection, the foreign key column is in the collection table for the map value.
  • If the join is for a map key for a ManyToMany entity relationship or for a OneToMany entity relationship using a join table, the foreign key column is in a join table.
  • If the join is for a OneToMany entity relationship using a foreign key mapping strategy, the foreign key column for the map key is in the table of the entity that is the value of the map.

Default (only applies if a single join column is used.) The concatenation of the following: the name of the referencing relationship property or field of the referencing entity or embeddable class; "_"; "KEY".

nullableback to summary
public boolean nullable()

(Optional) Whether the foreign key column is nullable.

referencedColumnNameback to summary
public String referencedColumnName()

(Optional) The name of the column referenced by this foreign key column. The referenced column is in the table of the target entity.

Default (only applies if single join column is being used.) The same name as the primary key column of the referenced table

tableback to summary
public String table()

(Optional) The name of the table that contains the foreign key column.

  • If the join is for a map key for an element collection, the foreign key column is in the collection table for the map value.
  • If the join is for a map key for a ManyToMany entity relationship or for a OneToMany entity relationship using a join table, the foreign key column is in a join table.
  • If the join is for a OneToMany entity relationship using a foreign key mapping strategy, the foreign key column for the map key is in the table of the entity that is the value of the map.

Default:

  • If the map is for an element collection, the name of the collection table for the map value.
  • If the map is for a OneToMany or ManyToMany entity relationship using a join table, the name of the join table for the map.
  • If the map is for a OneToMany entity relationship using a foreign key mapping strategy, the name of the primary table of the entity that is the value of the map.
uniqueback to summary
public boolean unique()

(Optional) Whether the property is a unique key. This is a shortcut for the UniqueConstraint annotation at the table level and is useful for when the unique key constraint is only a single field.

updatableback to summary
public boolean updatable()

(Optional) Whether the column is included in SQL UPDATE statements generated by the persistence provider.